Unable to change widget default settings

I made the changes as instructed on your website and was then instructed to do the following:

<script> 
    (function(g,s,t,p,l,n){
      g["_gstpln"]={};
      (l=s.createElement(t)),(n=s.getElementsByTagName(t)[0]);
      l.async=1;l.src=p;n.parentNode.insertBefore(l,n);
    })(window,document,"script","https://cdn.guestplan.com/widget.js");
 	_gstpln.accessKey = "*************************************";
	_gstpln.color = "#CE487A";
	_gstpln.fabText = "Book a Table";
 </script> 
Copy the following code and paste it on your website (at the end of the HTML Body section)

Sadly your support is minimal at best and does not describe how to go about doing that and to be honest I am dumbfounded as to why it can’t be part of the plugin itself which is clearly designed only to link the account to the website. I use WordPress because of the vast array of plugins as my knowledge of HTML is extremely limited. Please help as I honestly don’t know what to do as the changes are minimal and really don’t warrant all the time I’ve wasted so far in failing to achieve anything.

The page I need help with: [log in to see the link]